Treating Equine Orthopedic Injuries with Stem Cells

Stem cells are becoming a popular treatment option for orthopedic injuries in horses.

Photo: The Horse Staff

When it comes to treatment options for orthopedic injuries, some horse owners jump at the chance to give a new one a try. One such treatment option that has many owners excited is stem cell therapy. At the at the 2011 North American Veterinary Regenerative Medicine Conference held June 2-4 in Lexington, Ky., Larry Galuppo, DVM, Dipl. ACVS, professor and chief of equine surgery at the University of California (UC), Davis, William R. Pritchard Veterinary Medical Teaching Hospital, explained to horse owners how stem cells are currently being used to treat orthopedic injuries in horses, and how the cells might be used in the future.

The Basics

Galuppo began his presentation with a brief overview of how stem cells are collected and where they're harvested from:

Bone marrow-derived stem cells (collected from the sternum or the hip);

Adipose-derived stem cells (collected via an incision near the horse's tailhead); and

Once the stem cells have been harvested, the aspirate (stem cells that have been collected) is proliferated until there are enough cells for a treatment (although there is not yet a hard and fast rule as to how many cells to use per treatment, many veterinarians use upwards of 10 million cells per injection), and the cells are either frozen and stored for future use or injected directly into the injured horse. The cells that are proliferated are called mesenchymal stem cells (MSCs). (Note: For more in-depth information about what stem cells are and how they help injured horses heal, take a peek at Stem Cells and Tissue Healing in Horses.)

Current Applications

Galuppo explained that there are several areas in which stem cell therapy has proved successful thus far; veterinarians are currently using stem cells on bone, tendon, ligament, and cartilage injuries. Although there still is not an overwhelming amount of peer-reviewed scientific research, anecdotal evidence and case studies suggest that stem cells have be used to successfully treat a number of orthopedic injuries, some of which Galuppo described in detail.

Deep Digital Flexor Tendons--The deep digital flexor tendon (DDFT) runs from the back of the knee (or hock) down around the navicular bone and inserts on the coffin bone in the foot.

This tendon acts as a "sling" for the back of the fetlock and pastern to help it bear the animal's weight. Injuries to the DDFT are some of the most common ailments performance horses face and unfortunately are some of the most serious.

Galuppo explained that when treated with traditional methods (cold therapy, poultice, wraps, stall rest, etc.), horses with DDFT injuries returned to their previous level of work about 29% of the time. Researchers have experimented with treating similar injuries with MSCs, stromal vascular fraction from fat or bone marrow aspirate concentrate (stem cells that have not been proliferated, but rather spun down to separate the stem cells from the rest of the bone marrow matter), and the majority of horses (up to 75% of horses that were diagnosed and treated early) were able to return to work.

Bowed Tendons--Galuppo was excited to report that stem cells have been observed to help heal bowed tendons as well. He stressed that while the injuries seem to take about the same amount of time to heal as when treated with traditional therapies, the stem cells seem to positively affect the quality of the healing. Galuppo added that the positive effect is best illustrated by a reduced reinjury rate when horses are treated with regenerative medicine techniques as compared to traditional therapy.

Joint Disease--Galuppo explained that stem cells are currently being tested for efficacy in horses with joint disease. He discussed one case study in which a 3-year-old racehorse presented with a torn meniscus (fibrous cartilage material between joints) and cruciate ligament (which helps stabilize the joint) which resulted in excessive concussion to the cartilage overlying the main weight-bearing area of the knee.

The colt's owners opted to experiment with a combination of stem cells and platelet-rich plasma (PRP, another regenerative therapy produced by the horse's blood), which were injected into the knee joint in an attempt to regenerate the damaged tissues.

Galuppo explained when the stem cells and PRP were mixed together with thrombin (an enzyme involved in blood clotting), they formulated a glue-like substance that filled the cracks in the damaged cartilage. This technology enhanced the potential for keeping the stem cells where they needed to be to promote healing: within the damaged cartilage.

Several treatments and a long rehabilitation later, the colt successfully returned to the racetrack. Galuppo reported that he was able to return to his previous level of work without any detrimental effects on the injured leg. He also noted that the colt's owners have continued stem cell injections into the colt's joint to try to help him remain injury free.

Although the use of stem cells and PRP on this particular injury yielded exemplary results, Galuppo stressed that these therapies remain experimental: "Would this have happened if we didn't do anything? I don't know."

Fetlock Injuries--Finally, Galuppo described a case in which veterinarians treated a young Warmblood stallion with stem cells and PRP for a fetlock injury. He explained that the 5-year-old horse developed a bone cyst on the main weight-bearing part of the fetlock after sustaining an injury during turnout.

The stallion's owners opted to use a combination of regenerative therapies to try to save the horse's career. The team at UC Davis first removed the dead cartilage and bone from within the fetlock joint before injecting stem cells and PRP into the affected area as the main treatment. Once the horse had recovered from surgery, the team used intraarticular (within the joint) stem cell injections, IRAP (interleukin-1 receptor antagonist protein, used to essentially block inflammation), and bisphosphonates (a type of drug designed to prevent bone loss).

After a good rehabilitation program, Galuppo reported that the horse recovered well and the fetlock injuries had minimal lasting impact. Most of the affected area had filled in with healthy tissue, he added. Galuppo noted that at this stage, the horse has returned to full training to return to his previous career as a jumper. While his initial prognosis was poor for this activity and it is still questionable if he will hold up, his current soundness and radiographic examinations do not preclude him from pushing forth.

Again, Galuppo cautioned that these therapies are in the relatively early stages of development and clinical testing.

"Each case is different," he said. "We'll never have a 'cookbook' to say, 'For this, do this.'"

Future Use

In addition to the current orthopedic uses for regenerative therapy, Galuppo suggested a few other functions that stem cells, in particular, might be useful for:

Regenerating damaged or diseased organs (such as the liver, kidney, or heart);

Treating developmental orthopedic disease; and

Treating laminitis (researchers have begun experimenting with stem cells for laminitis treatment; however, further research is needed before it becomes a mainstream treatment option for the disease).

Additionally, Galuppo explained that some owners of valuable stallions are starting to bank stem cell aspirates when the horse is young. Since stem cells are still viable after more than 30 years of being frozen, this could allow for possible treatment options later in life should a problem arise.

One point Galuppo made about all the injuries he described is that early treatment is key. Although stem cells have been used frequently as a "last ditch effort," he encouraged horse owners to seek treatment as soon as possible after the injury occurs. Additionally, Galuppo stressed the importance of a good quality and consistent rehabilitation program in conjunction with any injury--not just regenerative medicine. He noted that, essentially, the rehabilitation program can either make or break the recovery efforts.

"We can enhance our potential for success with early diagnosis and intervention," he said.

Finally, he issued a word of warning for owners considering stem cell therapy for their horses. some adverse reactions have been noted when the cells weren't used or injected properly, so Galuppo suggested finding a veterinarian with a good knowledge base about stem cells and how to work with them properly.

"You've got to have the tools and someone who knows how to use them," he said. "Deal with people who've been in the business for a long time and who know what they're doing."

About the Author

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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